Tunable filter based on MEMS, working method thereof and spectrometer

Abstract

The invention discloses an adjustable filter based on a micro-electro-mechanical system (MEMS), a working method of the adjustable filter and a spectrograph, and the adjustable filter comprises an MEMS reflector, a first lens, a second lens, a diffraction grating and a third optical element. Wherein the MEMS reflector is used for generating rotation based on triggering of an electric signal, rotating to different angles at different moments, and reflecting input light, so that the input light reaches the diffraction grating through the first lens and the second lens; the diffraction grating is used for diffracting the incident light with different wavelengths to different angles, and the diffracted light rays diffracted to different angles form output light through the third optical element; the output light is used for spectral analysis.

Description

Technical Field

[0001] The present application relates to the field of spectrometers, and in particular to an adjustable filter based on a micro-electro-mechanical system (MEMS), a working method thereof, and a spectrometer. Background Art

[0002] As an optical instrument, a spectrometer (analyzer) can obtain a spectrum by analyzing light of different wavelengths. It is currently applied to various aspects of production and life, such as environmental monitoring, medical analysis, etc. In practical applications, there are spectrometers based on detector arrays and spectrometers based on tunable filters. Among them, the spectrometer based on the detector array can obtain a longer wavelength tuning range when the detector array is large, but the detector array is relatively expensive. From a cost point of view, this type of spectrometer cannot be widely used. How to increase or widen the spectral scanning range of the spectrometer based on the tunable filter has become a technical problem that needs to be solved urgently. Summary of the invention

[0003] The present application provides a MEMS-based tunable filter and a working method thereof, and a spectrometer to at least solve the above technical problems existing in the prior art.

[0004] According to a first aspect of the present application, a tunable filter based on a micro-electromechanical system MEMS is provided, comprising: a MEMS reflector, a first lens, a second lens, a diffraction grating and a third optical element; wherein,

[0005] The MEMS reflector is used to rotate based on the triggering of the electrical signal, rotate to different angles at different times, and reflect the input light so that it passes through the first lens and the second lens to reach the diffraction grating;

[0006] The diffraction grating is used to diffract incident light of different wavelengths to different angles. The diffracted light diffracted to different angles forms output light through a third optical element; the output light is used for spectral analysis.

[0007] In one possible implementation manner, the third optical element is a reflector, which is used to reflect the light in the diffracted light that is perpendicular to the third optical element as output light.

[0008] In one possible implementation manner, the tunable filter further comprises a single light receiving optical fiber; wherein,

[0009] The third optical element is a focusing lens, which is used to focus the light with the same diffraction angle at a predetermined position on the focal plane;

[0010] The single light-receiving optical fiber is used to receive the light focused on the predetermined position to obtain output light.

[0011] In one embodiment, the tunable filter further comprises two or more light receiving optical fibers; wherein,

[0012] The third optical element is a focusing lens, which is used to focus light with different diffraction angles at different positions of the focal plane; each of the different positions corresponds to the two or more light receiving optical fibers;

[0013] The two or more light-receiving optical fibers are used to receive the light focused at their respective corresponding positions to obtain output light.

[0014] In one possible implementation manner, the adjacent distance between the two or more light-receiving optical fibers is determined based on the rotation angle of the MEMS reflector, the fringe density of the diffraction grating, and the focal length of the third optical element.

[0015] In one possible implementation manner, the spectrum scanning range of a spectrometer with a large number of light receiving optical fibers is greater than the spectrum scanning range of a spectrometer with a small number of light receiving optical fibers.

[0016] In one embodiment, the spectral scanning range of the spectrometer of the two or more light receiving optical fibers is N times the spectral scanning range of the spectrometer of the single light receiving optical fiber, where N is the ratio of the number of the two or more light receiving optical fibers to the single light receiving optical fiber.

[0017] In one possible implementation, the output light is subjected to spectral analysis after being photoelectrically converted and sampled by a photodetector.

[0018] According to a second aspect of the present application, a working method of a tunable filter based on a micro-electromechanical system (MEMS) is provided, the method comprising:

[0019] The MEMS reflector is rotated based on the triggering of the electrical signal, and the MEMS reflector is rotated to different angles at different times to reflect the input light, so that the input light passes through the first lens and the second lens to reach the diffraction grating;

[0020] The incident light of different wavelengths is diffracted to different angles by using a diffraction grating, and the diffracted light rays diffracted to different angles form output light through a third optical element; the output light is used for spectral analysis.

[0021] In one possible implementation manner, the third optical element is used to reflect the light in the diffracted light that is perpendicular to the third optical element as output light; wherein the third optical element is a reflector.

[0022] In one possible implementation manner, the tunable filter further comprises a single light receiving optical fiber; wherein,

[0023] Focusing the light with the same diffraction angle at a predetermined position on the focal plane by using the third optical element; wherein the third optical element is a focusing lens;

[0024] The single light-receiving optical fiber is used to receive the light focused on the predetermined position to obtain output light.

[0025] In one embodiment, the tunable filter further comprises two or more light receiving optical fibers; wherein,

[0026] A third optical element is used to focus light with different diffraction angles at different positions on the focal plane; each of the different positions corresponds to the two or more light-receiving optical fibers; and the third optical element is a focusing lens;

[0027] The two or more light-receiving optical fibers are used to receive the light focused at their respective corresponding positions to obtain output light.

[0028] The present application provides a MEMS-based tunable filter, including: a MEMS reflector, a first lens, a second lens, a diffraction grating, and a third optical element. By utilizing the MEMS reflector, the first lens, the second lens, the diffraction grating, and the third optical element, the spectral scanning range is widened. Since the MEMS reflector is small in size, the tunable filter of the present proposal occupies a small volume of the filter. Naturally, the spectrometer including the small volume filter is a spectrometer that occupies a small volume, that is, the spectrometer including the MEMS-based tunable filter in the present application is a small spectrometer.

[0029] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present application, nor is it intended to limit the scope of the present application. Other features of the present application will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] By reading the detailed description below with reference to the accompanying drawings, the above and other purposes, features and advantages of the exemplary embodiments of the present application will become readily understood. In the accompanying drawings, several embodiments of the present application are shown in an exemplary and non-limiting manner, wherein:

[0031] In the drawings, the same or corresponding reference numerals represent the same or corresponding parts.

[0032] Figure 1 A block diagram for implementing spectral analysis for a spectrometer;

[0033] Figure 2 It is a schematic diagram of the composition of a spectrometer based on rotation drive;

[0034] Figure 3The schematic diagram of the structure of the MEMS-based tunable filter in the embodiment of the present application is shown Figure 1 ;

[0035] Figure 4 The schematic diagram of the structure of the MEMS-based tunable filter in the embodiment of the present application is shown Figure 2 ;

[0036] Figure 5 The schematic diagram of the structure of the MEMS-based tunable filter in the embodiment of the present application is shown Figure 3 ;

[0037] Figure 6 A schematic diagram of the implementation flow of the working method of the MEMS-based spectrometer in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0038] In order to make the purpose, features, and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0039] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings. The described embodiments should not be regarded as limiting the present application. All other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of this application.

[0040] In the following description, reference is made to “some embodiments”, which describe a subset of all possible embodiments, but it can be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0041] In the following description, the terms "first\second" involved are merely used to distinguish similar objects and do not represent a specific ordering of the objects. It can be understood that "first\second" can be interchanged with a specific order or sequence where permitted, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

[0043] Figure 1 This is a block diagram of the spectrometer that implements spectral analysis. Figure 1 In the example, the input is all wavelength spectra, and the tunable filter (tunable filter or optical filter) selects a certain wavelength of light beam at the same time, and inputs the selected light beam to the photodetector. The photodetector converts the optical signal into an electrical signal and samples the converted data. The sampled data is analyzed to realize the analysis of the spectrum.

[0044] Among them, the spectrometer based on rotation drive is a kind of tunable filter. Figure 2 This is a schematic diagram of the structure of a spectrometer based on rotation drive. Figure 2 In FIG. 1 , the tunable filter includes a circulator, a diffraction grating, a lens L1, a lens L2, and a MEMS mirror. The input optical signal input is input through port 1 of the circulator and output from port 2. The collimated light output from port 2 hits point A on the diffraction grating. The diffraction grating diffracts light of different wavelengths to different directions. In this figure, taking the diffraction grating diffracting two different directions of light as an example: light with a wavelength of λ1 (solid line) and light with a wavelength of λ2 (dashed line), lenses L1 and L2 image point A on the diffraction grating onto the MEMS mirror. That is, lenses L1 and L2 make the light with a wavelength of λ1 (solid line) and the light with a wavelength of λ2 (dashed line) meet on the MEMS mirror. The rotation angle of the MEMS mirror can be adjusted. By adjusting the angle of the MEMS mirror, a specific wavelength can be selected to be reflected back to port 2 of the circulator and then output to port 3. The light output to port 3 can be converted from an optical signal to an electrical signal and sampled by a photodetector and then used for spectral analysis.

[0045] Exemplarily, when the MEMS reflector is rotated to the angle shown by the solid line, the light beam with wavelength λ1 is selected to be reflected back to port 2 of the circulator. When the MEMS reflector is rotated to the angle shown by the dotted line, the light beam with wavelength λ2 is selected to be reflected back to port 2 of the circulator. In layman's terms, for the angle to which the MEMS reflector is rotated at a certain moment, the light beam perpendicular to the angle is selected to be reflected back to port 2 of the circulator. Figure 2 In the embodiment, the MEMS reflector is located at the end, and the selection of a specific wavelength is achieved by rotating the MEMS reflector at the end.

[0046] exist Figure 2 In the above equation, the incident angle φ and diffraction angle θ1 of the diffraction grating and the wavelength λ must satisfy the following formula (1):

[0047] λ(θ1)=P(sinφ+sinθ1) (1)

[0048] In practical applications, the physical quantities that may be involved are: DB : It is the diameter of the light beam on the diffraction grating; D M : represents the diameter of the MEMS reflector; f1: represents the focal length of lens L1; f2: represents the focal length of lens L2; ​​M: represents the magnification of the L1-L2 lens, ψ: represents the full optical angle that the MEMS mirror can rotate; W range : represents the wavelength range of the tunable filter; λ0: represents the center point of the spectrometer scanning wavelength range; θ0: represents the diffraction angle corresponding to λ0; ξ: represents the filter based on the diffraction grating Bandwidth; P: expressed as the spacing between grating stripes.

[0049] The expression of the resolution bandwidth ξ of the filter is shown in formula (2):

[0050]

[0051] The expression of the dispersion coefficient α of the grating is shown in formula (3):

[0052]

[0053] It can be understood that the diameter of the light spot on the MEMS reflector is approximately equal to the diameter of the MEMS reflector. The diameter D of the light spot on the diffraction grating is equal to the diameter of the MEMS reflector. B The relationship between is related to the magnification of lens group L1 and L2. The magnification M of lens group L1 and L2 is D B / D M Based on this, the angular range of diffracted light that can be collected by the MEMS reflector is ψ / M. Thus, the expression of the wavelength tuning range of the tunable filter can be shown in formula (4):

[0054]

[0055] Theoretically, a tunable filter with high resolution and large wavelength tuning range is required. From formula (2), the smaller λPcosφ is, the higher the resolution is. However, the smaller Pcosφ is, the smaller formula (4) is, and the smaller the wavelength tuning range is. Take the following set of values ​​as an example, (P,λ0,D M ,φ,λ0,θ0ψ)=(1um,1.55um,1mm,50.8°,50.8°,10°), to achieve a wavelength resolution of 0.2nm, the beam diameter D B It must be greater than 9.8 mm (millimeter), but since the diameter of the MEMS reflector is usually about 1 mm, a 10X magnification is required. Substituting the physical quantity values ​​required by the above formula (4) into formula (4), it can be obtained that under the above values, the wavelength tuning range W of the tunable filter rangeAbout 11nm (nanometers). 11nm cannot meet the requirement of wide wavelength tuning range of spectrometer.

[0056] It can be seen that how to obtain a spectrum analyzer with a wide wavelength scanning range has become a technical problem to be solved urgently. In the present application, a spectrum analyzer with a wide spectrum scanning range is provided.

[0057] In the present application, a MEMS-based tunable filter is provided, comprising: a MEMS reflector, a first lens, a second lens, a diffraction grating and a third optical element; wherein,

[0058] The MEMS reflector is used to rotate based on the triggering of the electrical signal, rotate to different angles at different times, and reflect the input light so that it passes through the first lens and the second lens to reach the diffraction grating.

[0059] The diffraction grating is used to diffract incident light of different wavelengths to different angles. The diffracted light diffracted to different angles forms output light through a third optical element; the output light is used for spectral analysis.

[0060] In the present application, a MEMS reflector is arranged at the front end of the tunable filter, and a third optical element (which may be a focusing lens) is arranged at the end. By rotating the angle of the MEMS reflector, and coordinating the diffraction grating, the third optical element, and multiple receivers (such as multiple light-receiving optical fibers) and other optical devices, a spectrometer with a wide wavelength scanning range is obtained without consuming a lot of economic cost. The technical solution of the present application is highly reliable, easy to implement in engineering, and highly practical.

[0061] The composition or components of the MEMS-based tunable filter in this application can be found in the following Figure 3-Figure 5 shown. Figure 3-Figure 5 The three tunable filters shown are three implementation forms of the MEMS-based tunable filters of the present application, wherein the first lens L1 and the second lens L2 are used to image the light reflected by the MEMS reflector to the same point of the diffraction grating (point A in the figure).

[0062] Further, such as Figure 3 As shown, the third optical element may be a fixed mirror, which is used to reflect the light in the diffracted light that is perpendicular to the mirror and return it to its original path as output light.

[0063] like Figure 4 As shown, the tunable filter also includes a single light receiving optical fiber. The third optical element may be a focusing lens L3, which is used to focus light with the same diffraction angle at a predetermined position on the focal plane. The single light receiving optical fiber is used to receive the light focused at the predetermined position to obtain output light.

[0064] like Figure 5 As shown, the tunable filter also includes two or more light receiving optical fibers. The third optical element may be a focusing lens L3, which is used to focus light with different diffraction angles at different positions on the focal plane; each of the different positions corresponds to the two or more light receiving optical fibers. The two or more light receiving optical fibers are used to receive the light focused at their respective corresponding positions to obtain output light.

[0065] In the present application, the adjacent distance between one or more light receiving optical fibers is determined based on the rotation angle of the MEMS reflector, the fringe density of the diffraction grating, and the focal length of the third optical element. For details, please refer to the subsequent related descriptions.

[0066] In the present application, the spectral scanning range of the spectrometer with a large number of light receiving fibers is greater than the spectral scanning range of the spectrometer with a small number of light receiving fibers. Furthermore, the spectral scanning range of the spectrometer with two or more light receiving fibers is N times the spectral scanning range of the spectrometer with a single light receiving fiber, where N is the ratio of the number of the two or more light receiving fibers to the single light receiving fiber. Assuming that the number of light receiving fibers is 5, the spectral scanning range of the spectrometer with 5 light receiving fibers is N=5 times that of the spectrometer with a single light receiving fiber.

[0067] The output light obtained by the tunable filter in this application is Figure 1 Similarly, spectral analysis can be performed after photoelectric conversion by the photoelectric detector and sampling by the data sampling module. Figure 5 The MEMS-based tunable filter spectrometer shown can widen or increase the scanning range of the spectrometer and is regarded as a MEMS-based (wide) spectrometer. The working principle of the spectrometer can be found in Figure 1 The middle part is similarly described (photoelectric conversion, sampling, analysis and other processes), and the identical parts are not repeated here.

[0068] and Figure 2 The MEMS shown is different behind the grating. Figure 3-Figure 5 As shown, the MEMS is placed in front of the diffraction grating. Also, in the setting position, the MEMS is located at the front focus of the lens L1, and the grating is located at the back focus of L2. The third optical element is as shown in FIG. Figure 3 As shown, it is a reflector. Figure 4 and Figure 5 As shown, a focusing lens is arranged behind the diffraction grating as a third optical element, and one or more light-receiving optical fibers are arranged behind the focusing lens.

[0069] Figure 3 As the first implementation of the MEMS-based tunable filter of the present application, Figure 3In the tunable filter shown, the MEMS mirror is placed before the diffraction grating, which doubles the angular efficiency of the MEMS mirror. This is because the structure is designed so that when the MEMS mirror is rotated by an angle ψ, the angle of the reflected light can change by 2ψ.

[0070] exist Figure 3 In the design structure shown, the reflector - Fixed mirror only allows light with a diffraction angle φ1 to reach the output port 3. That is, the diffracted light beam perpendicular to the Fixed mirror is allowed to be reflected by the Fixed mirror and return to the output port 2 along the original path, pass through the circulator, and output from the output port 3. When the MEMS reflector rotates to the position of the solid line, the reflector sends λ0 in the input light (input) to the output end. When the MEMS reflector rotates to the position of the dotted line, the reflector sends λ1 in the input light (input) to the output end. Among them, the optical path of λ0 is along the optical axis of lenses L1 and L2, and forms an incident angle θ0 with the diffraction grating. If all parameter values ​​are the same as the previous set of exemplary parameters, then through the calculation of the above formula (4), it is obtained Figure 3 Under the structural design shown, the wavelength tuning range is about 22nm, which is about Figure 2 The structure shown is designed twice as high.

[0071] It should be noted that in Figure 3 In , the beam before lens L1 and after lens L2 is collimated. Figure 3 In the present invention, a dual fiber collimator can be used instead of a circulator to direct the output beam to a photodetector.

[0072] Figure 4 As a second implementation of the MEMS-based tunable filter of the present application, Figure 4 In the design shown, the optics preceding the diffraction grating are Figure 3 After the diffraction grating, the Fixedmirror is removed, and a focusing lens L3 with a focal length f3 is added. Lens L3 is used as the third optical element in this application. Figure 4 The optical fiber also includes a single light-collecting optical fiber, which is arranged at the focal plane E (Focal plane E) after the lens L3 to collect light with a diffraction angle φ1 as output light output for spectral analysis.

[0073] use Figure 4 In the design shown, each diffracted beam becomes a point on the focal plane. For light whose diffraction angle deviates from the original φ by Δφ, its image on the focal plane E will deviate from the optical axis f3 (Δφ). Figure 4In the figure, when the MEMS reflector rotates to different angles at different times, the incident light is reflected, and then passes through the first lens L1 and the second lens L2 to reach the diffraction grating. For example, when the MEMS reflector rotates to the position of the solid line, the λ0 light in the incident light (input) will enter the receiving fiber. When the MEMS reflector rotates to the angle of the dotted line, the λ1 light in the incident light will enter the receiving fiber. In other words, after the diffraction of the diffraction grating, the diffracted light beam with a diffraction angle of φ1 is focused on a point on the focal plane E, and a single receiving fiber receives the light focused on this point, thereby using the rotation of the MEMS angle to sequentially measure the components of each wavelength in the incident light. Sequentially means that at different times, each time the MEMS reflector rotates to an angle, only one of the corresponding wavelengths of the input is allowed to be received by the receiving fiber.

[0074] based on Figure 4 For the design shown in FIG. 1 , if all parameter values ​​are the same as the previous set of exemplary parameters, then by calculating the above formula (4), we can obtain Figure 4 Under the structural design shown, the wavelength tuning range is about 22nm, which is about Figure 2 That is, by placing the MEMS in front of the diffraction grating and two lenses (lens L1 and lens L2), and placing a single light-receiving optical fiber at the focal plane of lens L3, the spectral range that can be obtained in time sequence is determined by the scanning angle range of the MEMS reflector.

[0075] Figure 5 As the third implementation of the MEMS-based tunable filter of this application. Figure 5 In the example, two light-receiving optical fibers (referred to as optical fibers): optical fiber 1 and optical fiber 2 are set. When the MEMS reflector rotates to different angles at different times, the incident light is reflected, and then diffracted by the diffraction grating, and the diffracted light beam with a diffraction angle of φ1 is focused at a predetermined position 1 (the position corresponding to optical fiber 1) on the focal plane E, and optical fiber 1 receives the light focused at the predetermined position 1. The diffracted light beam with a diffraction angle of φ2 is focused at a predetermined position 2 (the position corresponding to optical fiber 2) on the focal plane E, and optical fiber 2 receives the light focused at the predetermined position 2. Therefore, by rotating the MEMS reflector and collecting light from the two optical fibers, the components of each wavelength in the incident light input can be measured in sequence.

[0076] However, there are requirements for the number of optical fibers and the distance between two adjacent optical fibers, as shown in the following scheme.

[0077] When only optical fiber 1 is provided, light with an incident angle of θ and a diffraction angle of φ1 reaching the diffraction grating must satisfy formula (5).

[0078] λ (1)(θ)=P(sinθ+sinφ1) (5)

[0079] λ (1) represents a series of wavelengths when the receiving optical fiber is optical fiber 1. To distinguish it from a series of wavelengths under optical fiber 2, it is called the first zone wavelength. It can be understood that its diffraction angle is equal to φ1. When the incident angle θ is When , M is the magnification, which is the division of the focal length of lens L2 and the focal length of lens L1. These wavelengths will be focused onto the optical axis of focal plane E in sequence and collected by the receiving optical fiber - optical fiber 1 for output to the photoelectric detector for photoelectric conversion.

[0080] If the second light-collecting optical fiber - optical fiber 2 is arranged on the left side of the optical axis on the focal plane E to collect light with a diffraction angle φ2, it needs to satisfy formula (6):

[0081] λ (2) (θ)=P(sinθ+sinφ2) (6)

[0082] λ (2) The wavelengths representing the light receiving fiber are Fiber 2, which is called the wavelength of the second zone. It can be understood that the diffraction angle is equal to φ2, and the incident angle is between On the focal plane E, the ideal design is to make the left edge wavelength of the first zone just connected to the right edge wavelength of the second zone. This is to avoid the problem of wavelength overlap caused by a large overlap between the left edge length of the first zone and the right edge wavelength of the second zone, and to avoid the problem of wavelength omission and discontinuity caused by a certain distance between the left edge length of the first zone and the right edge wavelength of the second zone. This design in which the left edge wavelength of the first zone is just connected to the right edge wavelength of the second zone can effectively double the wavelength range of the spectrum analyzer (spectrometer). In this way, the wavelength λ0 corresponding to the center of the first zone and the wavelength λ1 corresponding to the center of the second zone is There is a relationship as shown in formula (7):

[0083]

[0084] In formula (7), the relationship between the wavelengths of the two zone centers is obtained by taking the incident angle as θ0. If the diffraction grating operates near the Littrow angle, then Use the same parameters as in the previous example. If all parameters are the same as in the previous set of exemplary parameters, (φ2-φ1)=2 0 , the focal length of lens L3 is f3 = 30 mm, then under the constraint of the relationship shown in formula (7), the spacing between the two receiving optical fibers (optical fiber 1 and optical fiber 2) is about 1 mm. When the spacing between optical fiber 1 and optical fiber 2 is 1 mm, combined with formula (4), as shown in Figure 5The design shown can effectively expand the wavelength range by a factor of 2 to 44 nm.

[0085] So, it is understandable that Figure 4 On the basis of the above, when the spacing between two adjacent receiving optical fibers is 1mm, the wavelength range will increase by 22nm for each additional receiving optical fiber. For example, if two optical fibers are arranged in this way, the wavelength range is 2x 22 = 44nm. If three optical fibers are arranged in this way, the wavelength range is 3x 22 = 66nm. And so on, until the wavelength range meets the actual needs.

[0086] For example, in practical applications, if a wavelength range of 100 nm needs to be covered, five receiving optical fibers can be arranged in the above manner to obtain a spectrometer with a wavelength range of 5x22=110 nm and a wavelength tuning range of ±110 nm.

[0087] Figure 5 The description shown is based on the example of setting two light-receiving optical fibers. In addition, designs of setting 3, 4 or more light-receiving optical fibers are all within the scope of this application.

[0088] In summary, compared with a spectrometer with a spectral scanning range of 11 nm, the technical solution of the present application adopts Figure 3 , Figure 4 and Figure 5 By designing the tunable filter in any of the above schemes, a spectrometer with a wider spectral scan (22nm, 44nm) is obtained. Since the volume of the MEMS reflector is small, the volume of other optical devices is also small, so overall, the tunable filter in this application is a small tunable filter. The tunable filter in this application can be used as Figure 1 The tunable filter in the spectrometer shown realizes the analysis of the spectrum through photodetectors, data sampling, data analysis, etc.

[0089] Use this application Figure 3-Figure 5 Any of the MEMS-based tunable filter spectrometers shown in the specification can be regarded as a MEMS-based (wide) spectrometer. The spectrometer of the present application has the advantages of wide spectral scanning range and miniaturization, and can also be regarded as a MEMS-based broadband spectrometer. The broadband spectrometer of the present application can be widely used, has strong practicality and high feasibility.

[0090] The present application provides a spectrometer, comprising Figure 3-Figure 5 The adjustable filter of any scheme. In addition, it also includes a photoelectric detector for photoelectric conversion, a data sampling module for sampling electrical signals, a data analysis module for analyzing the sampled data, etc., so as to realize spectral analysis. For details, please refer to the above related instructions, which will not be repeated here.

[0091] The present application provides a working method of a MEMS-based tunable filter, such as Figure 6 As shown, the method includes:

[0092] S601: The MEMS reflector is caused to rotate based on the triggering of the electrical signal, and the MEMS reflector rotates to different angles at different times to reflect the input light so that the input light passes through the first lens and the second lens to reach the diffraction grating;

[0093] S602: diffracting incident light of different wavelengths to different angles using the diffraction grating, and the diffracted light diffracted to different angles forms output light via a third optical element; the output light is used for spectral analysis.

[0094] In one embodiment, the third optical element is used to reflect the light in the diffracted light that is perpendicular to the third optical element as the output light; wherein the third optical element is a reflector.

[0095] In one embodiment, the tunable filter further comprises a single light receiving optical fiber; wherein,

[0096] The light having the same diffraction angle is focused at a predetermined position on the focal plane by using the third optical element; wherein the third optical element is a focusing lens;

[0097] The single light-receiving optical fiber is used to receive the light focused on the predetermined position as output light.

[0098] In one embodiment, the tunable filter further comprises two or more light receiving optical fibers; wherein,

[0099] A third optical element is used to focus light with different diffraction angles at different positions on a focal plane; each of the different positions corresponds to the two or more light-receiving optical fibers; wherein the third optical element is a focusing lens;

[0100] The two or more light-receiving optical fibers are used to receive the light focused at their respective corresponding positions to obtain output light.

[0101] In one embodiment, the adjacent distance between the two or more light-receiving optical fibers is determined based on the rotation angle of the MEMS reflector, the fringe density of the diffraction grating, and the focal length of the third optical element.

[0102] In one embodiment, the spectrum scanning range of the spectrometer with a large number of light receiving optical fibers is greater than the spectrum scanning range of the spectrometer with a small number of light receiving optical fibers.

[0103] In one embodiment, the spectral scanning range of the spectrometer of the two or more light receiving optical fibers is N times the spectral scanning range of the spectrometer of the single light receiving optical fiber, where N is the ratio of the number of the two or more light receiving optical fibers to the single light receiving optical fiber.

[0104] In one embodiment, the output light is subjected to spectral analysis after being photoelectrically converted and sampled by a photodetector.

[0105] It should be noted that the working method of the MEMS-based tunable filter in the embodiment of the present application, since the principle of solving the problem by the working method is similar to the working principle of the aforementioned MEMS-based tunable filter, therefore, the implementation process and implementation principle of the working method of the MEMS-based tunable filter can refer to the description of the implementation process and implementation principle of the aforementioned MEMS-based tunable filter, and the repeated parts will not be repeated.

[0106] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A tunable filter based on a micro-electromechanical system (MEMS), characterized in that: include: A MEMS reflector, a first lens, a second lens, a diffraction grating and a third optical element; wherein, The MEMS reflector is used to rotate based on the triggering of the electrical signal, rotate to different angles at different times, and reflect the input light so that it passes through the first lens and the second lens to reach the diffraction grating; The diffraction grating is used to diffract incident light of different wavelengths to different angles. The diffracted light diffracted to different angles forms output light through a third optical element; the output light is used for spectral analysis.

2. The tunable filter according to claim 1, characterized in that: The third optical element is a reflector, which is used to reflect the light in the diffracted light that is perpendicular to the third optical element as output light.

3. The tunable filter according to claim 1, characterized in that: The tunable filter also includes a single light receiving optical fiber; wherein, The third optical element is a focusing lens, which is used to focus the light with the same diffraction angle at a predetermined position on the focal plane; The single light-receiving optical fiber is used to receive the light focused on the predetermined position to obtain output light.

4. The tunable filter according to claim 1, characterized in that: The tunable filter also includes two or more light receiving optical fibers; wherein, The third optical element is a focusing lens, which is used to focus light with different diffraction angles at different positions of the focal plane; each of the different positions corresponds to the two or more light-receiving optical fibers; The two or more light-receiving optical fibers are used to receive the light focused at their respective corresponding positions to obtain output light.

5. The tunable filter according to claim 4, characterized in that: The adjacent distance between the two or more light-receiving optical fibers is determined based on the rotation angle of the MEMS reflector, the fringe density of the diffraction grating, and the focal length of the third optical element.

6. The tunable filter according to claim 4, characterized in that: The spectrum scanning range of the spectrometer with a large number of light receiving optical fibers is greater than the spectrum scanning range of the spectrometer with a small number of light receiving optical fibers.

7. The tunable filter according to claim 4, characterized in that: The spectral scanning range of the spectrometer of the two or more light receiving optical fibers is N times the spectral scanning range of the spectrometer of the single light receiving optical fiber, where N is the ratio of the number of the two or more light receiving optical fibers to the single light receiving optical fiber.

8. The tunable filter according to any one of claims 1 to 7, characterized in that: The output light is subjected to spectral analysis after being photoelectrically converted and sampled by a photodetector.

9. A MEMS-based spectrometer, characterized in that: The MEMS-based tunable filter comprises any one of claims 1 to 8.

10. A method for operating a tunable filter based on a micro-electromechanical system (MEMS), characterized in that: The method comprises: The MEMS reflector is caused to rotate based on the triggering of the electrical signal. The MEMS reflector rotates to different angles at different times to reflect the input light so that the input light passes through the first lens and the second lens and reaches the diffraction grating. The incident light of different wavelengths is diffracted to different angles by using a diffraction grating, and the diffracted light rays diffracted to different angles form output light through a third optical element; the output light is used for spectral analysis.

11. The working method according to claim 10, characterized in that: The third optical element is used to reflect the light in the diffracted light that is perpendicular to the third optical element as output light; wherein the third optical element is a reflector.

12. The working method according to claim 10, characterized in that: The tunable filter also includes a single light receiving optical fiber; wherein, Focusing the light having the same diffraction angle at a predetermined position on the focal plane by the third optical element; wherein the third optical element is a focusing lens; The single light-receiving optical fiber is used to receive the light focused on the predetermined position to obtain output light.

13. The working method according to claim 10, characterized in that: The tunable filter also includes two or more light receiving optical fibers; wherein, A third optical element is used to focus light with different diffraction angles at different positions on a focal plane; each of the different positions corresponds to the two or more light-receiving optical fibers; wherein the third optical element is a focusing lens; and the two or more light-receiving optical fibers are used to receive the light focused at their respective corresponding positions to obtain output light.

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